<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>運算符</title>
<script>
var num1 = 1;//賦值運算符,將右邊的值賦給左邊變量,則變量擁有值
var num2 = num1 + 1;//加法運算
/*
* 常用算數運算符
* + : 加 例:1+2=3
* - : 減 例:2-1=1
* * : 乘 例:2*3=6
* / : 除 例:6/2=3
* % : 求余 例:5%2=1;
* ++ : 自增 例:a++等于a+1;++a
* -- : 自減 例:a--等于a-1;--a
* a++與++a的區(qū)別:前者先運算后+1;后者先+1后運算
*
* 常用賦值運算符
* += : a+=b等同a=a+b;
* -= *= /= %=類同
*/
var str1 = "Hello";//"Hello"與"Hello "為不同字符串
var str2 = "World";//"World"與" World"為不同字符串
var str3 = str1+" "+str2;//字符串的相加為字符串的拼接
var str4 = str1 + num2;//字符串與數字的相加,結果為字符串,相當于把數字轉換為字符串
</script>
</head>
<body>
<h2>結果查看</h2>
<p>
<script>
document.write("num1 = "+num1+"<br />"+"num2 = "+num2+"<br />");
document.write("str3 = "+str3+"<br />"+"str4 = "+str4);
</script>
</p>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>運算符</title>
</head>
<body>
<h1>結果:</h1>
<script>
/*
* 比較運算符,返回布爾值True或者false,比較結果正確True,反正false
* == : 比較數值相等
* === : 全等(數值和類型)
* != : 不等于
* > : 大于
* < : 小于
* >= : 大于等于
* <= : 小于等于
*/
var num1 = 7;//賦值運算
if(num1 == 7){//比較變量值和數值
document.write("True");//比較結果,正確是返回
}else{
document.write("False");//比較結果錯誤是返回
}
document.write("<br />");
if(num1 === "7"){//數值和類型均符合才為真
document.write("True");
}else{
document.write("False");
}
/*
* 邏輯運算符,返回True或false True:1 false:0
* || : 或(一1則1)
* && : 與(一0則0)
* ! : 非(!1則0,!0則1)
*/
document.write("<br />"+"邏輯與結果:"+(true||false));
document.write("<br />"+"邏輯或結果:"+(true&&false));
document.write("<br />"+"邏輯非結果:"+(!0));
/*
* 條件運算符
* boole?aa:bb 如果ture則aa否則bb
*/
document.write("<br />"+"條件運算結果:"+(1>2 ? true : false));
/*
*
*/
</script>
</body>
</html>
- Boolean對象可以檢查對象的邏輯結果(true/false)
- Boolean對象可以將非邏輯值轉換為邏輯值
- 只有對象 無初始值,0,-0,null,"",false,undefined,NaN 返回false,其他返回true
- 注意:字符串'0',"false"值是true,只有空字符串為false.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<style type="text/css">
.code{
color: gray;
border: 1px solid gainsboro;
font-size: 15px;
}
pre{
margin: 1em 0em 1em -19em;
font-family: "楷體";
}
.result{
color: gray;
background-color: ghostwhite;
font-size: 16px;
padding: 0.5em 1em;
}
h3{
color: red;
}
.result span:first-child{
display: block;
float: left;
width: 10em;
color: black;
}
</style>
<script type="text/javascript">
function objDisplay(eleId,obj){
if(typeof(eleId)!="string" || typeof(obj)!="object"){
alert("Function objDisplay() need the first parameter string and second object !")
}else{
var ele = document.getElementById(eleId);
if(!ele || !obj){
alert("Please check the parameter !")
}else{
for(i in obj){
var div = document.createElement("div");
for(var j=0;j<2;j++){
var span = document.createElement("span");
if(j==0) span.innerHTML = i+" : ";
else span.innerHTML = obj[i];
div.appendChild(span);
}
ele.appendChild(div);
}
}
}
}
</script>
</head>
<body>
<ul>
<li>
<h3>Boolean對象</h3>
<h4>代碼:</h4>
<div class="code">
<pre>
//新建boolean對象
var booEty = new Boolean();
//布爾值
var booDict={
"Boolean()":new Boolean(),
"Boolean(0)":new Boolean(0),
"Boolean(-0)":new Boolean(-0),
"Boolean(null)":new Boolean(null),
"Boolean('')":new Boolean(''),
"Boolean(false)":new Boolean(false),
"Boolean(undefined)":new Boolean(undefined),
"Boolean(NaN)":new Boolean(NaN),
"Boolean('0')":new Boolean('0'),
"Boolean(1)":new Boolean(1),
"Boolean('false')":new Boolean('false')
}
objDisplay("dict01",booDict);
</pre>
</div>
<h4>結果:</h4>
<div id="dict01" class="result"></div>
<hr />
<script>
//新建boolean對象
var booEty = new Boolean();
//布爾值
var booDict={
"Boolean()":new Boolean(),
"Boolean(0)":new Boolean(0),
"Boolean(-0)":new Boolean(-0),
"Boolean(null)":new Boolean(null),
"Boolean('')":new Boolean(''),
"Boolean(false)":new Boolean(false),
"Boolean(undefined)":new Boolean(undefined),
"Boolean(NaN)":new Boolean(NaN),
"Boolean('0')":new Boolean('0'),
"Boolean(1)":new Boolean(1),
"Boolean('false')":new Boolean('false')
}
objDisplay("dict01",booDict);
</script>
</li>
</ul>
</body>
</html>
